1. Field of the Invention
The field of this invention is ion channels or nanopores, particularly methods of measuring the ionic current flowing through ion channels or nanopores.
2. Background of the Invention
Methods of measuring the ionic current through a single ion channel are critical to the study of ion channels, which play pivotal roles in a variety of physiological processes. Through such methods, the processes underlying ion permeation and gating have been explored.
One approach for measuring the ionic current flowing through a single ion channel is the patch-clamp technique. In the patch-clamp technique, a small patch of membrane that includes an ion channel of interest is isolated at the tip of a glass micro-electrode. The ion current flowing through the isolated ion channel is then measured. This approach has been invaluable as a research tool, but suffers from limitations in certain circumstances. For example, not all ion channels of interest are accessible by patch-clamp techniques. In addition, patch-clamp techniques do not provide the ability to modulate the membrane component and thus explore the lipid/channel interactions that potentially affect current flow through the channel.
In an alternative approach that can overcome these limitations, the channel of interest is reconstituted in an artificial thin film device. Although several such devices have been developed since the 1960s, there is continued interest in new configurations that reduce capacitance, noise, and solution volume.
Relevant Literature
Of interest are Wonderlin et al., xe2x80x9cOptimizing planar lipid bilayer single-channel recordings for high resolution with rapid voltage stepsxe2x80x9d Biophys. J. (1990) 58:289-297; Brutyan et al., xe2x80x9cHorizontal xe2x80x98solvent-freexe2x80x99 lipid bimolecular membranes with two-sided access can be formed and facilitate ion channel reconstitution,xe2x80x9d Biochimica et Biophysica Acta, (1995) 1236: 339-344; and Kasianowicz, et al., xe2x80x9cCharacterization of individual polynucleotide molecules using a membrane channel,xe2x80x9d Proc. Natl. Acad. Sci. USA (1996) 93: 13770-13773.
Miniature thin film support devices and methods for using the same are provided. In the subject devices, an electrical communication means, e.g. a U tube, connects cis and trans chambers that are filled with an aqueous fluid. At the cis end of the electrical communication means is a conical aperture that is sealed with a thin film into which has been inserted a single nanopore or channel. The subject devices further include a means for applying an electric field between the cis and trans chambers. The subject devices find use in a variety of applications in which the ionic current through the inserted nanopore or channel is monitored or measured for a period of time, e.g. several hours, including the characterization of naturally occurring ion channels, the characterization of polymeric compounds, and the like.